JP3030520B2 - Image forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to relates to an image forming method for performing charging by using the bias voltage applied to the developing sleeve side to the image forming side of the photosensitive drum, particularly the photosensitive drum
Conductive toner on the developing sleeve arranged opposite to
While supporting the conductive toner using magnetic force.
And accumulate it on the upstream side of the developing position.
Forming a toner pool, and the toner pool causes the above-mentioned feeling.
The developing sleeve while rubbing the image forming layer of the optical drum;
The bias voltage for the developing sleeve applied to the
The present invention relates to an image forming method for charging an image forming body of the photosensitive drum by injecting the photosensitive drum into the photosensitive drum .

[0002]

2. Description of the Related Art Conventionally, a photoconductive drum formed by laminating a light-transmitting conductive layer and a photoconductor layer on a light-transmitting support,
Exposure means for generating a light output corresponding to the image information is provided,
The optical output of the exposure means is focused and a latent image is formed on the photoconductor layer (hereinafter, such a latent image forming step is referred to as exposure or exposure step), or at the same time or immediately after that, the photoconductor drum is disposed to face the photosensitive drum. An image forming apparatus is known in which the latent image is converted into a visible image (toner image) via a developing unit, and then the toner image can be transferred onto plain paper via a transfer roller or other transfer unit. (Hereinafter referred to as back exposure apparatus)

In this type of image forming apparatus, in order to further simplify the structure and prevent ozone generation and the like, and to prevent ground fogging, the image forming apparatus faces the photosensitive drum without providing an independent charger. While carrying the conductive toner on the developing sleeve arranged as described above, the conductive toner is accumulated on the upstream side of the developing position using a magnetic force to form a toner accumulation by a so-called magnetic brush, The image forming layer is configured to be charged by injecting a bias voltage applied to the developing sleeve side to the photosensitive drum side while rubbing the image forming layer by the toner accumulation.

[0004]

However, in such a device, the bias voltage cannot be set to a high voltage from the viewpoint of safety or the like, and the charge is injected through a conductive magnetic brush. The charging ability is lower than that of the charging method using corona discharge, and the device tends to reduce the diameter of the drum in order to reduce the size of the device, and the charging ability is further reduced.

[0005] Such a drawback becomes more remarkable when amorphous silicon is used for the photoconductor layer of the drum, especially when the power is turned on or when the printing operation is stopped for a predetermined time and then restarted. A predetermined time (a predetermined number of rotations of the drum) until the trapped charges are sufficiently accumulated, a fog (a phenomenon in which toner adheres to the background portion) occurs during development of the toner image. This results in the transfer of a dirty image to the recording material.

The present invention has been made in view of the drawbacks of the prior art, and
Conductive on the developing sleeve located opposite the optical drum
While carrying the conductive toner, the conductive toner is
Using force to accumulate on the upstream side of the developing position,
A toner pool is formed by a brush, and the toner pool is
While rubbing the image forming layer of the photosensitive drum.
Developing sleeve bias applied to image sleeve side
A voltage is injected into the photosensitive drum side to
It is an object of the present invention to provide an image forming method for charging an image forming body, which enables clear development and smooth transfer to a recording material side without fogging from the initial stage of startup.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a photosensitive drum.
Conductive toner on the developing sleeve arranged opposite to
While supporting the conductive toner using magnetic force.
And accumulate it on the upstream side of the developing position.
Forming a toner pool, and the toner pool causes the above-mentioned feeling.
The developing sleeve while rubbing the image forming layer of the optical drum;
The bias voltage for the developing sleeve applied to the
In the image forming method for charging the image forming body of the photosensitive drum by injecting it into the photosensitive drum side, the bias voltage for the transfer unit applied to the transfer unit can be switched between forward and reverse to start the image forming operation. time or a predetermined time at the time of re-start-up, said that during the transfer process to a bias voltage having the same polarity for the developing sleeve to apply a bias voltage for the transfer means opposite polarity to the transfer means, the bias voltage for the developing sleeve using a bias voltage for the transfer means together to raise the charge level of prior said imaging member the image forming operation starts by performing charging of said image forming body, for the developing sleeve to said transfer means after said predetermined time A bias voltage for the transfer unit having a polarity opposite to a bias voltage is applied to the transfer unit.

That is, a transfer means for transferring the toner image carried on the image forming body of the photosensitive drum to the recording material side is effectively used, and after the start-up (re-starting), the image is formed on the image forming body. predetermined time the recording material is supported until transferring the toner image, the bias voltage of the same polarity voltage is applied to the transfer means, said image forming body by using a voltage applied to said transfer means together with said bias voltage Is characterized in that it is charged. The present invention is particularly effective for an apparatus using amorphous silicon for the photoconductor layer of the image forming body, because the trap is deep and therefore the time until the charge is accumulated tends to be long. Not done.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention; However, unless otherwise specified, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention, but are merely illustrative examples. Not just.

FIG. 1 shows an overall configuration of an image forming apparatus according to an embodiment of the present invention. Reference numeral 1 denotes a photosensitive drum, which is formed of a light-transmitting conductive layer 1b and amorphous silicon on a drum-shaped light-transmitting support 1a. And a rotatable photoconductor layer 1c in the direction of the arrow.

Reference numeral 2 denotes an exposure unit inserted in the photosensitive drum 1, and an LED array 22 for generating a light output corresponding to image information on a support 21 made of a non-translucent insulating material. An exposure system consisting of a lens 23 (trade name: Selfoc lens) and an eraser 24 extending in the axial direction of the photoreceptor at the opposite side of the support 21 in the circumferential direction are fixed. Are located. The image forming position of the exposure system is configured to form an image on the photoconductor layer 1c located on the focal line connecting the photosensitive drum 1 and the axis of the developing sleeve 31 described later.

Reference numeral 3 denotes a developing device, which has an opening on a side facing the photosensitive drum 1 of a toner container 32 for accommodating a conductive magnetic toner, and has a developing sleeve 31 containing a fixed magnet assembly 34 in the opening 33. By rotating the sleeve 31 in the direction of the arrow, the toner whose layer thickness is regulated by the doctor blade 36 formed on the container 32 side is exposed to the exposure system 2.
It is configured to be guided to the developing position corresponding to the image forming position 2-23. The sleeve 31 is connected to a bias power supply 8 for generating a half-wave rectified voltage on the positive side. still,
The photoconductor drum 1 and the developing sleeve 31 are configured to be rotatable in opposite directions in a region where both face each other.

Reference numeral 37 denotes a toner pool formed on the upstream side of the developing position of the photosensitive drum 1 by a fixed magnetic pole included in the developing sleeve 31. The toner pool 34 is rubbed by the developing sleeve 31 on the surface of the photosensitive drum 1. A bias voltage applied to the sleeve 31 through the interface is injected into the photosensitive drum side to perform uniform charging.

Reference numeral 4 denotes a transfer roller composed of a conductive rubber roller, which is connected to a power supply circuit 10 capable of switching half-wave rectification between forward and reverse, and is configured to be rotatable and rotatable in synchronization with the photosensitive drum 1.

Next, the configuration of the power supply circuit 10 will be described with reference to FIG. D1 to D4 are diodes for generating half-wave rectification, R1 and R2 are protection resistors, 11 is an AC power supply, 12 is a power switch, 13 is a changeover switch,
4 is a relay for operating the changeover switch 13;
5 is a transistor switch for controlling the energization of the relay 14, and 16 is a fuse.

Next, the operation of the embodiment will be described. First, after the power is turned on by turning on the power switch 12, the photosensitive drum 1 is rotated, and at the same time, the bias power supply 8 is turned on, and an initial signal H (ON) is applied to the base side of the transistor switch 15.

As a result, the changeover switch 13 is switched to the A side via the relay 14, and a positive half-wave rectified voltage having the same polarity as that of the bias power supply 8 is applied to the transfer roller 4. In this state, without performing exposure / development on the photosensitive drum 1, the bias voltage is injected into the photosensitive drum 1 via the conductive toner reservoir 37 formed on the upstream side of the developing position, and a predetermined voltage is applied. Since the charging is performed and the conductive transfer roller 4 to which the half-wave rectified voltage having the same polarity as the bias voltage is applied is rotating in contact with the photosensitive drum 1, the charging is also performed from the roller 4 side. Therefore, even when the photoconductor layer 1C is formed of amorphous silicon, a sufficient amount of charge is quickly and sufficiently accumulated in a deep trap portion of the silicon.

After the initial charging step has been performed for a predetermined time, more specifically, until the photosensitive drum has been rotated two or three times, a transfer signal L (OFF) is applied to the base side of the transistor switch 15. As a result, the changeover switch 13 is switched to the B side via the relay 14, and a negative half-wave rectified voltage having a polarity opposite to that of the bias power supply 8 is applied to the transfer roller 4.

In this state, the toner image is carried on the photosensitive drum 1 by performing exposure / development on the photosensitive drum 1 using the exposure unit 2 while continuing charging by the toner pool. It is guided to the transfer position side. At the transfer position, a negative half-wave rectified voltage having a polarity opposite to that of the charged toner is transferred from the back side of the recording material inserted through the transfer roller 4 with a timing by a registration roller (not shown) with a certain timing, thereby enabling smooth transfer. Becomes

Next, the effect of this embodiment will be described with reference to the graph of FIG. FIG. 3A shows the number of rotations of the drum and the surface potential V of the photosensitive drum when charging is performed based on this embodiment.
and (b) shows the fog frequency when development was performed in that state. On the other hand, FIG.
The relationship between the drum rotation speed and the photosensitive drum surface potential Vp when the transfer voltage is turned off without charging from the side, in other words, without applying a voltage of the same polarity, and charging is performed only with the bias voltage. And (d) shows the fog frequency when development was performed in that state.

As is clear from the above graphs, when the transfer roller side is also charged, it reaches a region where fogging disappears at the second rotation after the rotation of the drum. The region where fogging finally disappeared at the rotation eyes was reached, and the effect of the present invention was clearly demonstrated.

[0022]

As described above, according to the present invention, charges can be accumulated in the trap immediately after the start of the image forming operation, and clear development without fogging can be formed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a main configuration of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration of a transfer voltage power supply circuit illustrated in FIG. 1;

FIGS. 3A and 3C are graphs showing a relationship between a drum rotation speed and a surface potential in the present embodiment and a comparative example.
(B) and (d) are graphs showing the relationship between the number of rotations of the drum and the fog frequency when development is performed in that state.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor drum 31 Developing sleeve 4 Transfer roller 8 Bias power supply 10 Transfer voltage power supply circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 15/02 G03G 15/05 G03G 15/16 G03G 13/02

Claims (2)

(57) [Claims] 1. A developing device arranged to face a photosensitive drum.
The conductive toner is carried on the sleeve, and the conductive toner is
Using a magnetic force to transfer the conductive toner to the upstream side of the developing position
Accumulate to form a toner pool with a magnetic brush,
The image forming layer of the photosensitive drum is slid by the toner accumulation.
While rubbing, the developing sleeve applied to the developing sleeve side is
Inject a bias voltage for leave into the photosensitive drum side
In the image forming method for charging an image forming body of the photosensitive drum, a transfer unit bias voltage applied to the transfer unit is configured to be switchable between forward and reverse, and a predetermined voltage may be set when starting up or restarting the image forming operation. Time, the transfer unit bias voltage having the same polarity as the developing sleeve bias voltage and having the opposite polarity to that during the transfer process is applied to the transfer unit, and the transfer unit bias voltage together with the developing sleeve bias voltage is applied. Utilizing the charging of the image forming body, the charging level of the image forming body is increased prior to the start of the image forming operation, and the transfer means is provided to the transfer unit after the predetermined time.
An image forming method, wherein a bias voltage for a transfer unit having a polarity opposite to a bias voltage for a developing sleeve is applied to the transfer unit. 2. The image forming method according to claim 1, wherein amorphous silicon is used for a photoconductor layer of the image forming body.